[clang] [Serialization] Use 32 bit aligned decl id instead of unaligned decl id (PR #95348)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

@alexfh Could you try to test this? And if this doesn't mitigate it, it will be helpful to provide the hotspot.

https://github.com/llvm/llvm-project/pull/95348